We have discovered and characterized a new member of the MS family of nucleotides. We propose to investigate the effect of this nucleotide on the synthesis of ribosomal and transfer RNA, and its possible feedback effects on the stringent factor reaction. We have identified a new genetic locus, relX, involved in the metabolic control of ppGpp synthesis; we propose to look for the activity of the relX gene product in vitro. We propose to continue our investigation of the mechanism of mistranslation in relA mutant cells, and the kinetics of error propagation in vivo.